https://www.vision-systems.com/cameras-accessories/article/1...
You're already extracting as much information you can from the analog signal on the least significant bits. It's not like designing a log-scale ADC lets you pull more information from the least significant bits. So you don't really have anything to gain. Why make a more complicated analog circuit to extract less information? It's generally better to let the digital side decide what to keep, how to compress the signal, etc.
And I should mention that CMOS camera sensors can often do a lot of digital processing right there on the chip. So you can do log-scale conversion or whatever you want before you send the data out of the CMOS camera chip.
It might be possible that you could reduce the power consumption of a SAR (successive approximation) ADC by skipping AD conversion of less significant bits if you have signal on the more significant bits. But I doubt the power savings would be very significant.
A linear ADC with enough range is usually fine, you can do the math later. But maybe for this case it needs a non-linear element before the ADC? (no idea how log recording needs anything at the HW level)
hardware accelerated HDR on cameras are commonplace these days, especially in dashcams and CCTV cameras.
Maybe people are just starting to get sick of this argument being used against everything.
The comment I replied to didn't go nearly that far, but it's an argument I've seen so often that I feel compelled to point out that "consumers" are not the only target audience for Apple - they are trying to also market themselves to creators, as well as professionals, and they absolutely know the difference and notice when things like these become available.
Well, I don't think "people" generally do that. It's nothing to do with stupidity; just lack of need and interest.
> The comment I replied to didn't go nearly that far
Not just "didn't go that far", it wasn't anything to do with that. It was just articulating pleasant surprise.
If I were to return this thread to its objective origin, I would agree that if you're selling a mass-market device, it's surprising to cater to a fractional percentage of that user base. I don't see how that's contentious.
I argue it shouldn't be that surprising because a lot of people find value in this 1%, and each person wants a different 1%.
But maybe it's surprising because most companies are stupid and don't realize this.
And it's entirely possible that they got to the point that they are now saying pro stuff is cool. Even is 99.x % of users won't really use it.
If your darkest pixel is halfway down the ADC range, on linear you're throwing away one bit, on logarithmic you're throwing out way more bits. Just using higher bit linear ADC then converting it to logarithmic in post-processing seems more sensible. Hell you could even go signal magic and merge few photos with different shutter speed together to get most detail.
Also proper log-to-in converter like AD8307 costs like $20 so I'd assume doing that woudl bring the sensor price way up if you needed to have a bunch of them.
Encoding audio with different log-scale companding has been around for some time too (since the 1970's) with A-law and mu-law in G.711.
(does that mean there is a crossover in the middle of amplitude range that shows LSBs of one of ADCs poking their heads, I mean, in a hypothetical ultra-naive implementation?)
The best implementations have a dynamic range of about 140-150 dBA. Floating point is not needed to achieve that and it isn't always used (look at Stagetec products).
from a super high level all ADCS do is quantize an analog signal. They take in a voltage from say 0 - 1.8V and quantize that on a 12 bit range. Return a value from 0-4095. You could build one that scales this range with non-linear steps. But this doesn't add any value. We won't get more accuracy at smaller steps. Our noise and accuracy problems won't be solved by this as they are due to thermal noise or mismatch. quantization noise is not the problem. (We already build segmented ADCs to try and do this)
It's not my area so would love to correction from someone who is deep in the space. My current perception is the 32 bit float hype in the audio capture world is the marketing reality distortion field in effect. Having that representation expand further upstream than the DSP or DAW makes sense, but it's not magic. Even in 32 bit float there's only 24 bits of precision (assuming IEEE 754).
What is interesting, useful, and lost in that noise is devices have refined the multi-ADC design to enable full usage of that precision matched to the overall dynamic range of the analogue front-end. Previously the ADC would be the bottleneck, but that's now shifted to the upstream circuitry or transducer.